Abstract: A coupling assembly comprises an input shaft driven by a prime mover, at least one output shaft drivingly coupled to the input shaft, a fluid pump selectively driven by the input shaft through an auxiliary clutch, a friction clutch for selectively frictionally coupling the input shaft with the at least one output shaft, and a fluid clutch actuator for operating the friction clutch between a disengaged condition and an engaged condition. The fluid pump selectively communicates with the fluid clutch actuator for setting the friction clutch assembly in the engaged condition. The fluid pump is mounted to the input shaft.

Abstract: There is provided a control device for a vehicular power transmitting apparatus of equipped with a differential portion is provided for suppressing a durability decrease of the differential portion or component parts related thereto upon preventing a rotary element of the differential portion from reaching a high-speed rotation. Rotation-stop determining means 72 makes a query as to whether the first rotary element RE1 is lowered in a rotation speed to be stopped during an engine drive mode. If the answer is YES and differential-portion rotation speed determining means 74 makes a positive determination, then engaging-element control-executing means 78 executes engaging element control. This allows a third rotary element RE3 of the differential portion 11, connected to drive wheels 38 via an engaging element of an automatic shifting portion 20, to approach a state available to freewheel.

Abstract: When an engine stop control is executed while an automatic ratio shift portion is in a neutral state, a switching clutch is operated, so that a differential portion carrier of a differential portion planetary gear device that is linked to an engine, and a differential portion ring gear linked the automatic ratio shift portion are integrally rotated. Therefore, along with the engine stop control, the rotation speed of the rotating elements of the differential portion planetary gear device is reduced while the rotating elements are integrally rotated or substantially integrally rotated. Since the rotating elements are rotated integrally or substantially integrally, the high rotation speed of the differential portion ring gear linked to the automatic ratio shift portion, which tends to have a heightened rotation speed particularly during the neutral state, is prevented.

Abstract: A drive apparatus for vehicle, available to be minimized, is provided. A first planetary gear set (differential device) 24 through which an output of a drive power source is distributed to a first electric motor M1 and a transmitting member 18, and a switching clutch C0 and a switching brake B0 operative to selectively place the first planetary gear set 24 in a differential state to function as an electrically continuously variable transmission and a locked state, are disposed between the first electric motor M1 and a second electric motor M2. This enables a power transmitting state to be performed in a broad range. Additionally, as the first planetary gear set 24 is placed in the locked state under a high output region of an engine to transfer the engine output to drive wheels mainly through a mechanical power transmitting path, an electrical reaction force to be guaranteed with the first electric motor M1 can be reduced, enabling the first electric motor M1 to be minimized.

Abstract: This invention relates to a control device for a vehicular power transmitting device. The control device has shifting-point altering means 108 operative such that when a second electric motor M2 is operated with priority to obtain a charging efficiency and/or electric power generating efficiency, a shifting point for a vehicle to run under a decelerating state (during a coast running state) is altered to a point on a higher vehicle speed than that at which a shifting point for a running-performance-conscious state is set. Therefore, when the second electric motor M2 is operated with priority for generating electric power, a downshift is initiated at a high vehicle speed than that at which the downshift is initiated at a shifting point for a running-performance-conscious state. This increases a rotation speed NM2 of the second electric motor M2, resulting in an increase in regeneration amount (electric power generation amount) of the second electric motor M2.

Abstract: A four-wheel drive system for a hybrid vehicle includes at least two motor-generators and a single engine connected to a differential having multiple degrees of freedom. In some embodiments, by adjusting the outputs of the motor-generators, a controller allocates power from the engine, to or from each of the motor-generators, to the front wheels and to the rear wheels, each of which is connected to an element of the differential. The relationship between the elements of the differential is represented by an alignment chart of the differential.

Abstract: The present invention provides a system for providing an improved compact power transfer unit for use in motor vehicles having a front wheel drive transverse based engine and transaxle, and, more particularly, to a power transfer unit for use with a transaxle arrangement capable of providing all-wheel drive or four-wheel drive. The present invention discloses a planetary gear utilizing a fixed ring gear, the planetary gear capable of selectively engaging a low range output from the power transfer unit for propelling the vehicle when driven in off-road conditions requiring higher torque and slower speeds. The vehicle driver can selectively engage a normal, high range where torque flows through the planetary gear directly to the drive shaft with no gear reductions, or the driver may selectively engage the low range where the torque flowing into the planetary gear is redirected and reduced thereby providing higher torque with reduced speed.

Abstract: The present invention provides a method for improving cornering performance. From a given vehicle speed and lateral acceleration, in instances of a decrease in drive torque, individual wheel torque is shifted from inside wheels to outside wheels to increase vehicle yaw forces and counteract the understeer phenomenon. Similarly, in instances of increasing drive torque, individual wheel torque is shifted from outside wheels to inside wheels on a common axle to reduce vehicle yaw forces and counteract the oversteer phenomenon. Actual implementation of side-to-side torque shifting is done using a correction factor multiplied by other factors within a general torque shift equation.

Abstract: When a reduction in a supply hydraulic pressure to a second shift portion is sensed, an engagement command of C0 clutch is generated so that a power split device (electrical differential portion) is brought into a locked state. In the locked state, a sun gear, a carrier rotated by an engine and a ring gear rotated by a second MG integrally rotate, whereby inertia is increased. Thus, high-speed rotation of a transmission member corresponding to an input shaft of the second shift portion can be prevented.

Abstract: A method for controlling a power assisted propulsion system in a motor vehicle so as to perform a transition from a lower gear to a higher gear without interrupting a driving torque applied to driving wheels; the propulsion system displays an internal combustion engine provided with a drive shaft and a power assisted transmission comprising in turn: a power assisted mechanical gearbox provided with a primary shaft connectable to the drive shaft and a secondary shaft connected to a transmission shaft which transmits motion to the driving wheels; a power assisted clutch interposed between the drive shaft and the primary shaft of the gearbox to connect and disconnect the drive shaft to the primary shaft of the gearbox; a power assisted brake; and an epicycloidal gear having three rotating elements: a first rotating element connected to the drive shaft, a second rotating element connected to the secondary shaft of the gearbox, and a third rotating element connected to the brake.

Abstract: In a control apparatus of a vehicular drive system, a charging/discharging-restricted shift control apparatus makes a determination to perform a shift in a shifting portion such that less power is charged to a power storage device or discharged from a power storage device when charging or discharging of the power storage device is restricted than when charging or discharging of the power storage device is not restricted.

Abstract: A control device for a vehicular drive system including a differential portion (11) having a differential mechanism (16) operable to distribute an output of an engine (8) to a first electric motor (M1) and a power transmitting member (18), and a second electric motor (M2) disposed in a power transmitting path between the power transmitting member and a drive wheel (38) of a vehicle, the control device including a differential limiting device (C0, B0) provided in the differential mechanism (16) and operable to limit a differential function of the differential mechanism for thereby limiting a differential function of the differential portion (11), and torque-response control means (84) for controlling a response of a change of an input torque of the differential portion to an operation of a manually operable vehicle accelerating member (45), depending upon whether the differential function of the differential mechanism (16) is limited or not.

Abstract: The application aims at determining the locked or unlocked state of a differential (10). According to a first aspect, the determination is carried out on basis of a speed difference of output shafts (16, 18) using speed sensors (36, 38). Steering angle may be used as further input. In a second aspect, a sensing system (70) senses actuating pressure, voltage or current of an actuating mechanism (44). In a third aspect, the first and second aspects can be combined.

Abstract: Method and differential-lock control apparatus for differential lock control are disclosed. A control unit is arranged for communication with an engine speed sensor, a differential-lock activation control, and a differential lock. The control unit is adapted to allow for reduction of an engine speed to a desired engine speed if the engine speed is at least a threshold engine speed in response to receipt of an activate-differential-lock request signal, and adapted to subsequently output an activate-differential-lock control signal to the differential lock so as to command activation of the differential lock.

Abstract: A differential score protection system that regulates an engine to inhibit damage to a differential driven by the engine includes a first module that initiates a differential score protection mode and a second module that decreases an engine speed when the engine speed exceeds an engine speed limit. The engine speed limit is one of a plurality of pre-determined values based on a design slip speed limit of the differential.

Abstract: The invention is directed to a transmission that controls multiple torque generating elements. The transmission control device utilizes two torque generating elements that are connected to an output element through a differential which has two degrees of freedom and at least three rotating elements. The transmission can use the inertia response of the torque generating elements during a change in a command value of a demanded driving force and improves the ability to increase and decrease the output driving force and the responsiveness of any increase or decrease of the driving force.

Abstract: Method and device for providing, in an engine-driven goods vehicle, at least two driving wheels (9, 10, 51, 52) and at least one differential (5, 6, 45, 46, 47) arranged between the driving wheels (9, 10, 51, 52). The device includes an engine control unit (3), at least one differential lock (7, 8, 48, 49, 50) for locking or braking the differential (5, 6, 45, 46, 47), the differential lock (7, 8, 48, 49, 50) being arranged between the driving wheels (9, 10, 51, 52). An operating element (4, 44) for activating each of the differential locks (7, 8, 48, 49, 50). The engine control unit (3) being configured to read-off the position of the operating element (4, 44) and to limit positive or negative output torques of the engine (1) when activating at least one of the differential locks (7, 8, 48, 49, 50) and as a function of the transmission ratio prevailing in the transmission (2, 42).

Abstract: An actuation enhancement for an automated vehicle inter-axle differential (IAD) locking system. The vehicle having an engine and a tandem drive axle. The IAD actuation enhancement locking system comprises a rotating sliding clutch and a rotating side helical gear, which are capable of an engagement mode and a disengagement mode, a microprocessor, and an electrical connection between the microprocessor and an engine electronic control unit. When the sliding clutch and the helical gear are placed in the engagement mode or are placed in the disengagement mode, the microprocessor momentarily communicates a data link message to the engine electronic control unit to break engine torque, to facilitate engagement or disengagement of the sliding clutch and the helical gear.

Abstract: A temporary indicated torque is obtained by taking a conventional dead zone area for a first slip control area, and the value proportional to the slip quantity for a maximum value, this temporary indicated torque is corrected by a correction value according to the tight cornering brake quantity to be the indicated torque of the transfer clutch, and occurrence of any tight cornering brake phenomenon is prevented thereby. In a slip control area after passing a dead zone area (a second slip control area), the slip control is smoothly transferred from the first slip control area to the second slip control area by performing the slip control with a value of the indicated torque according to the slip quantity added to the indicated torque in the first slip control area as the indicated torque, abrupt torque change is prevented, and the vehicle behavior is stabilized thereby.

Abstract: A target command generator for use in a control system for an automatic transmission having a simple planetary gearset in series with a multiple-ratio gearset, the target command generator providing input for a controller for the simple planetary gearset to achieve synchronized control of pressure operated friction elements of the gearsets to effect smooth swap-shifts during an overall transmission ratio change.

Abstract: In a differential limiting torque control section, a target differential rotation speed between front and rear drive shafts is established according to a dial position inputted by a driver of a variable dial. Further, an actual differential rotation speed between front and rear drive shafts is calculated and a deviation between the target differential rotation speed and the actual differential rotation speed is calculated. Based on the deviation, a first differential limiting torque and based on a dial position of a variable dial a second differential limiting torque are calculated. Further, a third differential limiting torque is calculated based on the dial position and a throttle opening angle. A final differential limiting torque between front and rear drive shafts is obtained by summing up these first, second and third differential limiting torques.

Abstract: A drive-force distribution controller controls a drive-force transmission apparatus of a vehicle in order to control transmission of drive force to rear wheels or front wheels of the vehicle in accordance with a designated drive-force transmission ratio. The drive-force transmission ratio is changed on the basis of vehicle speed, differential rotational speed (speed difference between the front and rear wheels), and throttle opening. Alternatively, the drive-force transmission ratio is changed on the basis of vehicle speed, throttle opening, and throttle open speed. The change speed of current which is supplied to the drive-force transmission apparatus in order to control the drive-force transmission ratio is adjusted in accordance with a command current filter value which is determined on the basis of vehicle speed and a command current filter map of a vehicle-speed responsive type.

Abstract: A speed change control method of controlling a speed change ratio of a continuously variable transmission mechanism including a traction continuously variable transmission, includes: estimating a tilt angle of a power roller included in the continuously variable transmission based on an input rotating speed and an output rotating speed of the continuously-variable transmission mechanism; estimating a position of the power roller based on an estimated tilt angle obtained by the tilt angle estimating step and a command signal given to a driving device of adjusting the tilt angle of the power roller; and executing a feedback control operation based on an estimated position of the power roller obtained by the position estimating step.

Abstract: A power transfer apparatus 1 of a four-wheel drive vehicle includes, a clutch, an inversion detector, and controller. The clutch generate an engagement force that effects a driving force output from an engine to wheels of the vehicle via a transmission. The transmission includes the inversion detector 23, 27 for detecting inversion or non-inversion of a gear-shifting direction of the transmission 13. The controller 23 subjects the electromagnet to energization control such that torque to be transmitted by the clutch is decreased to a target value in accordance with an inversion signal pertaining to said gear-shifting direction detected by said inversion detector 23, 27.

Abstract: A system for adjusting the tension of a continuous part of a continuously variable transmissions; which is adjustable preferably with respect to its transmission ratio, the continuously variable transmission being mounted together with a vehicle engine and at least one clutch and a vehicle engine in the drive train of the vehicle, the clutch having various operating states. The essence of the invention is the adjustment of the tension at least in dependence upon the operating state of the clutch. The adjustment of the tension of the continuous part is especially advantageous when it is undertaken in dependence upon whether an adjustment of the transmission ratio of the continuously variable transmission takes place toward higher transmission ratios or to lower transmission ratios. Furthermore, the adjustment of the tension can take place in dependence upon the activation of an ABS system, ASR system and ESP system.

Abstract: A drive-force distribution controller for a four-wheel-drive vehicle in which drive force produced by an engine is transmitted directly to front or rear wheels and is transmitted to the remaining wheels via a torque distribution clutch, and the engagement force of the torque distribution clutch is controlled in accordance with traveling conditions of the vehicle. The controller includes a calculation unit for calculating variation per unit time in rotational speed difference between the front wheels and the rear wheels; and a control unit for controlling the engagement force such that the engagement force increases as the variation per unit time in the rotational speed difference increases.

Abstract: A differential coupling (20) has a body (21), a rotary input member (22), and two rotary output shafts (23, 24). The algebraic sum of the angular displacements of the output shafts is proportional to the rotation of the input member. The improvement includes mechanical means (39), such as a planetary gear (42), for sensing a torque differential between the output shafts, and a brake (38) mounted on the body and operatively arranged to selectively brake rotation of the input member, or both output members, when the difference between the torques on the outputs exceeds a predetermined first value.

Abstract: In driving force controlling apparatus and method for a four-wheel drive vehicle, a command is outputted to a front-and-rear wheel driving force distribution control system to reduce a clutch engagement force of a clutch such as a frictional clutch when a subtraction value of a detected value of a clutch transmission torque from that of a clutch input torque (Tinp−Tr) is smaller than a predetermined value (&dgr;) and detected wheel velocities of both of left and right road wheels of the vehicle are substantially equal to each other (Vw1±&agr;=Vw2 and Vw3±&agr;=Vw4).

Abstract: A transfer case control system or apparatus 10 is provided for use on a four-wheel drive vehicle of the type having a transfer case 32, a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 is communicatively coupled to sensors 44, 46, 48, and to a transfer case 32. Controller 40 selectively generates a control signal having a proportional term or component and an integral term or component. The control signal is generated to transfer case 32 and controls the amount of torque provided to driveshafts 22, 26.

Abstract: The present invention provides a method and apparatus for determining the cross slope created by a work implement on a work machine operating in an articulated or non-articulated manner. The method includes the steps of determining a position of the work implement, determining a direction of travel of the machine, and responsively determining the cross slope.

Abstract: An integrated system for automatically controlling the operation of both an automated mechanical transmission and a multiple speed axle assembly in a vehicle drive train assembly includes a transmission actuator for operating the transmission in any one of a plurality of transmission gear ratios. The system further includes an axle actuator for operating the axle assembly in any one of a plurality of axle gear ratios. An electronic controller is provided for operating the transmission in a desired one of the plurality of transmission gear ratios and for operating the axle assembly in a desired one of the plurality of axle gear ratios to provide a desired overall gear ratio for the vehicle. To accomplish this, the electronic controller is responsive to one or more input signals that represent operating parameters of the vehicle.

Abstract: A system for controlling the operation of a multiple speed axle connected to an automated transmission system is disclosed. The system includes an actuation device that cooperates with a processing unit to prevent the transmission from shifting gears while the axle shift is being performed. In one embodiment, once transmission shifting is prevented, the axle shift operation is performed manually by the vehicle operator, such that the vehicle operator manipulates the vehicle throttle to interrupt torque and synchronize the axle for engagement. The automated transmission then notifies the operator that the transmission is in a hold mode until the operator determines that the axle shift has been completed. The operator then manually returns the transmission to the drive mode to resume normal automatic transmission shifting. In a second embodiment, the axle shift operation is automatically performed by the processing unit.

Abstract: An adaptive torque control and distribution system for a motor vehicle having a transfer case, primary driveline and drive wheels and secondary driveline and drive wheels for operation in extreme off road conditions such as sand. The transfer case includes a modulating clutch and a lockup clutch disposed in parallel between its primary (rear) output and secondary (front) output. The system detects abnormally high magnitude and rapidly repeating wheel spin transients which are characteristic of operation in sand or similar highly randomly variable tractive conditions and overrides the on demand torque distribution program for a predetermined time interval. During this predetermined time interval, the transfer case lockup clutch is activated thereby coupling the primary and secondary drivelines and achieving a fifty-fifty torque split therebetween while the modulating clutch is inactive.

Abstract: A motor vehicle power train includes an engine (26) mounted longitudinally near the front of the vehicle and a transmission assembly (35) mounted intermediate front and rear differentials (17, 18). The transmission assembly is connected to the engine through an input propshaft (31), to the front differential through a front propshaft (37) and to the rear differential through a rear propshaft (38). The transmission assembly comprises a change speed transmission (28) which receives drive from the input propshaft and a hollow output shaft (49), a transfer transmission comprising a center differential (30) which is drivably connected to the hollow output shaft, has a front differential output shaft (54) for transmitting drive to the front propshaft and a rear differential output shaft (56) for transmitting drive to the rear propshaft, one of the differential output shafts (54) extending co-axially through the hollow output shaft.

Abstract: An adaptive torque control and distribution system for a motor vehicle having a transfer case, primary driveline and drive wheels and secondary driveline and drive wheels for operation in extreme off road conditions such as sand. The transfer case includes a modulating clutch and a lockup clutch disposed in parallel between its primary (rear) output and secondary (front) output. The system detects abnormally high magnitude and rapidly repeating wheel spin transients which are characteristic of operation in sand or similar highly randomly variable tractive conditions and overrides the on demand torque distribution program for a predetermined time interval. During this predetermined time interval, the transfer case lockup clutch is activated thereby coupling the primary and secondary drivelines and achieving a fifty-fifty torque split therebetween while the modulating clutch is inactive.

Abstract: A driving-torque control system for a four-wheel-drive vehicle includes a transfer clutch employed in a transfer of the four-wheel-drive vehicle for varying a distribution ratio of driving torque between front and rear road wheels depending on a front-and-rear wheel revolution-speed difference. A calculation unit derives a command value of the engaging force of the transfer clutch from the front-and-rear wheel revolution-speed difference. A load-condition detection unit detects an input load condition of the transfer clutch, on the basis of the front-and-rear wheel revolution-speed difference and the command value of the engaging force. A comparing unit compares the input load condition detected by the load-condition detection unit with a predetermined threshold. A compensation unit compensates the engaging force of the transfer clutch so that the transfer clutch is held in a completely engaged state for a predetermined holding time duration, when the input load condition exceeds the predetermined threshold.

Abstract: In a vehicle drive system having a torque split arrangement, it is difficult to have all the rotating parts of the system to be properly balanced. In particular, when a rotational speed difference is produced between the two output elements, relatively massive parts which may not be properly balanced may have to be turned at a high speed. According to the present invention, because the power output of the engine is reduced whenever any significant speed difference is produced between the two output elements, no part of the drive system is subjected to any excessive rotational speed, and are therefore not required to have any excessive mechanical strength. This improves the reliability of the system, and reduces the manufacturing cost.

Abstract: A control system for engaging, disengaging and re-engaging a front wheel drive in an agricultural vehicle includes a control circuit configured to receive signals representative of vehicle operating parameters and to generate control signals corresponding to the desired state (i.e. engaged or disengaged) of a front wheel drive engagement circuit. Sensors are associated with the rear wheels, rear service brakes, implement positioning circuit, the vehicle body and the front axle to provide parameter signals related to wheel speed, braking, implement position and vehicle speed. Control logic executed by the control circuit in a continuously cycled routine determines the desired state of the engagement circuit based upon all operating parameters. The control circuit applies an appropriate control signal to the engagement circuit causing engagement or disengagement in accordance with the desired state.

Abstract: A subpump assists a main pump for feeding hydraulic oil into a vehicle transmission system so as to control the distribution of the drive force transmitted to front and rear wheels. A motor for driving the subpump is started with a predetermined timing and energized for a predetermined drive time, so that the subpump circulates hydraulic oil with air which is mixed into the hydraulic oil by a chain that is turned in an oil tank, from a strainer chamber for the subpump, to prevent accumulation of air in the oil tank.

Abstract: A differential unit having a speed-sensitive-type differential limiting function is capable of moderating the differential limiting force to maintain the controllability and stability of a vehicle. The differential unit according to the present invention includes a differential case to be rotated by drive force of an engine, a differential mechanism for distributing rotations of the differential case to a pair of output shafts, a frictional clutch for limiting the differential of the differential mechanism, a hydraulic actuator for clutching the frictional clutch, an oil pump which receives differential torque of the differential mechanism so as to be driven to operate the hydraulic actuator, control valves for introducing air to the oil suction portion of the oil pump, and a controller for opening or closing the control valve to correspond to a condition under which a vehicle is driven.

Abstract: A power transfer system is disclosed for a four-wheel drive vehicle operable for permitting a vehicle operator to select between various full-time and part-time four-wheel drive modes. The power transfer system includes a dual-planetary gear reduction unit that is operable for establishing high-range and low-range speed ratios, and a powershift mechanism that is adapted to permit the vehicle operator to shift on-the-fly for establishing full-time and part-time high-range and low-range four-wheel drive modes. The power transfer system includes an slip limiting/torque-biasing arrangement including an interaxle differential and a mode clutch operable for controlling the magnitude of speed differentiation and torque biasing across the interaxle differential.

Abstract: A geared steering device (30) selectively operates rightside and leftside driving mechanisms (2,3) of a crawler vehicle (1) for more efficient operation of the crawler vehicle. The geared steering device (30) comprises a power input drive element (33) for inputting a driving power from a prime mover (7), rightside and leftside steering brakes (38R, 38L), rightside and leftside direct-coupled clutches (36, 44), a turn clutch (46), three arrays of planet gear trains (40, 43 and 48), and power output shafts (32R, 32L) coupled to right and leftside steering brake hubs (34R, 34L). A control unit compares an actual steering ratio of a geared steering device (30) with a designated steering ratio, outputs control signals to respective solenoid valves for controlling the direct-coupled clutches, the turn clutch or a steering brake so as to cause the actual steering ratio to approximate the designated steering ratio.

Abstract: An automatic four-wheel-drive vehicle having a multiple-ratio transmission with a torque output shaft connected drivably to a rear driving axle and a transfer gear box having a front drive shaft connected drivably to a front axle, the transfer case providing a four-wheel low-drive mode, a neutral mode and a two-wheel-drive/automatic four-wheel drive mode, an electric motor adapted to shift the transfer case from one mode to another mode and an electronic controller responsive to predetermined driving conditions for effecting an automatic shift of the transfer case from either a forward drive mode or a reverse drive mode to the neutral drive mode whereby the vehicle is conditioned for towing by interrupting the torque flow path from the rear drive wheels of the vehicle to the transmission mechanism and transfer case.

Abstract: A control system/method for determining vehicular gross combined weight (GCW) is provided. GCW is determined immediately after upshifts of a transmission (10) and requires only input signals indicative of engine or driveline torque (DL), vehicle acceleration (dOS/dt) and currently engaged gear ratio (GR).

Abstract: A restrictive control system for a differential which drives both drive axles at the same time but allows them to turn at different speeds during turning. The system variably generates a restrictive force, with which the differential is restricted in differential action, during turns. The restrictive force is reduced when a change in engine load is detected which is greater than a predetermined value and a steering angle is detected which is greater than a predetermined angle.

Abstract: A differential control system for restrictively controlling a differential, which has electromagnetically controlled clutches disposed between differentially driven shafts, is electromagnetically controlled to lock and unlock the driven shafts. The control system has a controller for restrictively applying a locking current to the differential to lock and unlock the clutches in accordance with control modes manually selected.